Ratchet-jack



R. G. CLARK.

RATCHET JACK,

APPLlCATiON FILED NOV. 17. 1920. 1

Patented Nov. 8, 1921.

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353 @Jctomwgy R. G. CLARK.

RATCHET JACK,

APPLICATION HLED NOV. 17. 1920.

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Patented Nov. 8, 1921.

UNITED STATES:

PATENT OFFICE.

ROBERT G. CLARK, OF BROOKLYN, NEW .YORK.

nATcHE'r- Acx.

To all whom it may concern:

Be it known that I, ROBERT G. CLARK, a citizen of the United States, and a resident of the borough of Brooklyn, in the county of Kings and city and State of New York, have invented a new and useful Ratchet- Jack, of which the following is a specification.

The object of the invention is to provide a simple and eflicient ratchet jack operated by continuous rotary movement of an operating shaft.

In the accompanying drawings forming a part hereof:

Figure 1 is an elevation of a jack embodying the invention, looking at the backs of the pawls and face of the ratchet bar;

I Fig. 2 is an elevation looking at right angles to Fig. 1;

Fig. 3 is a fragmentary side elevation of the pawl and ratchet mechanism, one-half of the frame being cut away;

Fig. 4 is a similar View, showing a different position of the pawls;

Figs. 5 and 6 are horizontal sections on the lines 55 and 66 of Fig. 3, respectively; and

Fig. 7 is an elevation on a larger scale of the operating shaft andcams.

The frame of the jack is marked 1, and the ratchet toothed jack-bar movable therein is marked 2. A horizontal rotary operating shaft 4 journaled in hearings in the side of the frame has a projecting portion 5 to receive an extension handle.

Two pawls 6 work side by side opposite the toothed face of the bar in an appropriate chamber of the frame. Each pawl has a tooth 7 at its upper end to coact with the teeth of the bar, and some distance below its tooth is formed with a substantially square hole 8. Within these openings are oppositely disposed cams 9 on the shaft, each cam being generally three-sided, with its sides and corners rounded, the cams being arranged with narrow portions near the axis of rotation and broad bi-laterally symmetrical basal portions disposed outwardly therefrom. As indicated in Fig. 7, the corners of each of these cams are formed on arcs struck with equal short radii from three interior points forming an equilateral triangle, one of these points being the center of the shaft; while the sides are formed on arcs struck from and at the opposite sides of the same points, with equal long radii,

Specification of Letters Patent.

Application filed November 17, 1920. Serial No. 424,590.

the two radii being substantially equal to the Width of the square opening.

The lower portions 10 of the pawls are bifurcated or slotted to cooperate with an intermediate fixed rib or abutment 11 on the frame, so that the abutment limits the movement of said lower portions in both horizontal directions, toward and from the ratchet bar, the space between the bifurcations of the pawls being materially wider than the rib.

To lift, the cams are rotated in a counterclockwise manner in Figs. 3 and 4, and to lower, in a clockwise direction. Owing to the nature of the cams and the frames with which they cooperate, the pawls are actuated by a rectangle of movement, with dwells at top and bottom where the exchange of pawls with the rack takes place. The mechanism is self-holding and cannot run down. In the lifting operation the alternate encounter of the rear portions of the tails of the pawls with the abutment compels their teeth to enter the ratchet-bar at the proper time preparatory to lifting. During lowering the inner portions of the tails strike against the abutment and compel the pawls to swing out from the ratchet at the proper moment prior to rising clear of the bar to enter its teeth at a higher point. Springs are not required. When the cams are up and down as in Fig. 4, both pawls can be swung out from the ratchet-bar by pushing in the accessible rear portions of their tails, thus enabling the jack-bar to be dropped quickly when the load has been lowered to a support.

The advantages of the jack will be apparent to those skilled in the art. Modifications in respect to form, proportions and reversals may be made without departing from the essential character of the invention.

What I claim as new is:

1. A jack, comprising a ratchet-bar, two pawls having square openings, and rotary operating means having two three-sided cams working in said openings, substantially as described.

2. In a ratchet jack, lifting and lowering mechanism comprising two pawls having square openings, rotary operating means having two three-sided cams working in said openings, and fixed means cooperating with the lower portions of the pawls, substantially as described.

3. In a ratchet jack, lifting and lowering 4. In'a ratchet jack, lifting and lowering '10 mechanism comprising two pawls having square openings, rotary operating meanshaving two three-sided camsworking in said openings, and an abutment cooperating with the lower portions of the pawls, said abutment limiting the movement of said portions in both forward and rearward directions, substantially as described;

havingtwo three-sided cams working in said openings, and a fixed rib, the lower portions of the pawls being bifurcated'or slotted so as'loosely to embrace saidrib, substantially as described.

"mechanism comprising two pawls having,"v

square 'open1ngs,i:rotary operating means ROBERT e. CLARK. 7 

